Losing weight on a cruise? Sounds impossible. With gourmet food on tap, snacks served 24 hours a day, and a temptation to ditch exercise altogether - it's a combination that makes cruising one of the most potentially damaging holidays for your waistline.

[Read more: 10 tips for staying safe on a cruise holiday]

But three celebrities have set sail across Europe in the new Lorraine summer special Lorraine’s Cruise Control, which follows X Factor winner Sam Bailey, comedian Helen Lederer and Gogglebox’s Sandi Bogle aboard a cruise ship on the Mediterranean and see them swap their usual daily lives for a week of workouts, balanced diets and mindful reconditioning.

Hosted by TV presenter and life coach Jeff Brazier and celebrity fitness trainer Faisal Abdalla, the celebrities will set sail from Venice aboard a P&O Cruises ship visiting Ravenna, Italy, Dubrovnik, Croatia, Valetta and Malta.

Also joining them on board will be Lorraine’s fashion expert Mark Heyes who will be suggesting fashion for the celebs and Dr Hilary who will be keeping their health in check.

Speaking about why she was taking part in Lorraine’s Cruise Control,  Sam Bailey said: "I want to be a role model for my kids, I hate eating broccoli, but have had to learn to love it, so they see me eating it.

"I also want to lose a dress size - I can’t currently see my toes - and want to lie on the beach without people mistaking me for a whale!"

But how easy is it really to lose weight while you're on a cruise, if you don't have the experts to hand?

Authors of Cruise Yourself Slim Martin and Marion Shirran, who are both weight-management specialists and avid cruisers, have come up with a series of suggestions to avoid gaining additional body ballast while sailing the high seas.

1. Eat tempting food first

Firstly, they recommend eating food you find most tempting first rather than piling plates high with the intention of leaving the best until last. That way, you'll feel full quicker and won't overeat.

[Read more: 9 reasons why cruises are great for families]

2. Use a small plate

Using a smaller plate is also a good habit to adopt; research shows that people can eat up to 30% more when they use a larger plate.

3. Remember, the buffet is a diet danger zone

Buffets are well-known danger zones, so it's best to either ask a partner to select dishes or keep temptation literally out of sight. Research has confirmed that the further away a person sits from the food at a buffet, the less likely they are to overeat.

4. Ask yourself if you're really hungry - or just bored

Another handy tip is to focus on the words 'want' and 'need' to determine whether you are actually hungry or simply bored.

5. Skip the lift and take the stairs

Lack of activity is one of the main causes for weight gain, and on a cruise ship, you may only burn 600 calories a day - the equivalent value of a Pina Colada.

Sitting down burns just one calorie per minute, while walking up and down stairs burns 10 calories. So take the opportunity to walk where possible. Strolling around the deck is not only a good way to admire the views, but it will help you stay in shape as well.

Do you find yourself putting on weight on holiday? Share your tips for staying slim in the comments box below.